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A091815
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Numbers n such that numerator of sum(i=1,n,(i-1)/i) is prime.
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0
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3, 4, 5, 6, 7, 9, 11, 13, 15, 16, 17, 22, 61, 69, 73, 97, 120, 125, 138, 141, 158, 180, 183, 220, 224, 317, 370, 457, 517, 546, 573, 648, 678, 692, 699, 804, 848, 1182, 1213, 1225, 1300, 1866, 2093, 2344, 2411, 2837
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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Select[Range[3000], PrimeQ[Numerator[Sum[(i-1)/i, {i, #}]]]&] (* Harvey P. Dale, Jul 13 2011 *)
Position[Accumulate[Table[(k-1)/k, {k, 3000}]], _?(PrimeQ[Numerator[#]]&)]// Flatten (* Harvey P. Dale, Jun 06 2021 *)
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PROG
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(PARI) ss(n)=sum(i=1, n, (i-1)/i); for (i=1, 1200, if(isprime(numerator(ss(i))), print1(i, ".")))
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CROSSREFS
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KEYWORD
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hard,nonn
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AUTHOR
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Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 07 2004
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EXTENSIONS
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More terms from Harvey P. Dale, Jul 13 2011
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STATUS
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approved
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